Information may be stored on thermoplastic carrier material in the form of high resolution relief patterns such as phase holograms or diffraction gratings. The thermoplastic carrier material may be in the form of a card, tape, or sheet. The embossed relief pattern, which illustratively includes video information or authenticity information, may be read using available optical devices.
An apparatus for embossing holograms onto a thermoplastic carrier is disclosed in U.S. Pat. No. 3,758,649. this apparatus, an embossing mold,formed as an endless belt, and a thermoplastic information carrier are jointly passed between two calender rollers, one of which is heated. The thermoplastic carrier is heated to a sufficient temperature so that the relief pattern carried by the mold is transferred to the thermoplastic information carrier.
Another apparatus for embossing high resolution relief patterns onto a thermoplastic material is disclosed in U.S Pat. No. 4,125,760. U.S. Pat. No. 4,125,760 also discloses an embossing mold shaped as an endless belt, which embossing mold is passed through a pair of rollers along with the thermoplastic carrier material.
U.S. Pat. No. 3,855,025 discloses an arrangement in which thermoplastic tape is passed around a heating cylinder having a heating band mounted under tension thereon.
It is an object of the present invention to provide an improved apparatus for embossing high resolution relief patterns onto thermoplastic carrier materials. More particularly, it is an object of the present invention to provide an embossing apparatus which permits the achievement of relatively high working speeds while minimizing distortions in the embossed relief patterns which would prevent the recovery of information to be stored in the relief patterns.